An embodiment of an apparatus according to the opening paragraph is known from WO 00/10166. The known apparatus for reading information recorded on a track of a data carrier comprises a transducer for generating a detection signal in response to the recorded signal on the data carrier. The apparatus has correction means for correcting radial tilt. Radial tilt is an obliquity of the data carrier in a plane oriented transversely to the part of the track that is read by the transducer and transversely to the data carrier.
The apparatus further has error signal generating means for generating an error signal for the correction means. The error signal generating means calculate the error signal from a correlation between a first auxiliary signal and a second auxiliary signal and from the correlation between the first auxiliary signal and a third auxiliary signal, which auxiliary signals are derived from the detection signal. The second and the third auxiliary signal are estimates of the recorded signal. The first and the third auxiliary signal respectively have a first delay and a second delay with respect to the second auxiliary signal, the magnitude of the delays corresponding to the duration of one revolution and two revolutions of the data carrier.
The correction means as described in WO 00/10166 comprises actuators for changing the radial tilt orientation of the transducer with respect to the data carrier. Also a transparent plate can be used which by tilting this plate in radial direction can change the radial tilt error.
An other embodiment of an apparatus according to the opening lines is known from WO 00/10165. The known apparatus for reading information recorded on a track of a data carrier comprises a transducer for generating a detection signal in response to the recorded signal on the data carrier. The apparatus has correction means for correcting tangential tilt. Tangential tilt is obliquity of the data carrier in a plane oriented parallel to the part of the track that is read by the transducer and transversely to the data carrier.
The apparatus further has error signal generating means for generating an error signal for the correction means. The error signal generating means are adapted to derive the error signal for the error signal from a temporal asymmetry of the response of the read signal to recorded signal.
The correction means as described in WO 00/10165 comprises actuators for changing the radial tilt orientation of the transducer with respect to the data carrier. Also a transparent plate can be used which by tilting this plate in radial direction can change the radial tilt error.
When the data carrier has a tilt error, a wobble of the data carrier in a direction transverse to the data carrier is introduced when the data carrier is rotated. This results in a focused reading spot with dynamic coma aberrations in both the radial and tangential directions. Disc reading performance of the transducer given the continuously changing radial and tangential tilt levels is thus very poor, even with the correction means of the known apparatus.